The development of instruments and methods for chemical analysis at the femtomole level has allowed physiologists to obtain better understanding of the transport process of the kidney. Specifically, scientists have been able to measure the transport of mammalian kidney tubule for two metabolites, ammonium ion and lactate. The work done under this project concerns the further development and improvement of the fiber optic microfluorimeter and extensionn of its use from ammonium ion to lactate. The fluorimeter has been improved by replacing the shorter live 85 watt mercury lamp with a 200 watt lamp and better light collection optics. In addition, a slow speed pump has been added to allow measurement of lactate by an enzymatic reaction producing the fluorescent material, NADH. Both ammonium and lactate can be measured with femtole sensitivity. The new optics has permitted the replacement of the previously used phtomultiplier with a solid state photodiode. In addition, work has been started on the development of a constant but adjustable speed pump suitable for the 0.5 to 5 microliter/min rates required by the microanalysis chemistries involved.